# Rainfall Calculator vs Thetis Tools

The clearest difference is price: Thetis Tools at Free against Rainfall Calculator's $2.99. Thetis Tools also leads on update cadence (every 7 months vs every 29 months). Rainfall Calculator's advantage is chart position (#176 vs unranked). On ads, in-app purchases, device support and iOS requirement there is nothing between them.

Thetis Tools is free to download; Rainfall Calculator costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Rainfall Calculator ships an update every 29 months, Thetis Tools every 7 months. The most recent releases landed on September 9, 2026 and September 10, 2026 respectively.

## The numbers

| Metric | Rainfall Calculator | Thetis Tools |
| --- | --- | --- |
| Price | $2.99 | **Free** |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/rainfall-calculator/id1446150880/reviews)** | — |
| Number of ratings | **1** | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 29 months | **Every 7 months** |
| Monetization | Paid | — |
| Best chart rank | **#176** | — |
| Size | 1 MB | 50 MB |
| Requires iOS | **13** | 14.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Nitrio](https://appshunter.io/developer/321121189) | [Thetis srl](https://appshunter.io/developer/397584184) |

## What reviewers say

### Rainfall Calculator

[App page](https://appshunter.io/ios/app/rainfall-calculator/id1446150880)

**Currently charting:** #176 Top Paid · Productivity (US App Store)

Calculate potential rainwater harvest volume and cost savings. This tool helps determine annual water collection capacity based on rainfall and roof area, recommending optimal tank sizes for efficient water storage. It also allows for cost-saving analysis by comparing harvested water to mains water prices.

**Highlights:** Instant rainwater calculation, Cost savings evaluation, Minimum tank size recommendation, Supports various input units, Formula references included, Results copyable to other apps

**Features:** macOS Compatibility

**In-app purchases:** none


### Thetis Tools

[App page](https://appshunter.io/ios/app/thetis-tools/id1460268980)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Rainfall Calculator free?

Rainfall Calculator costs $2.99, with no in-app purchases.

### Is Thetis Tools free?

Thetis Tools is free to download, with no in-app purchases.

### Do Rainfall Calculator or Thetis Tools have ads?

Neither Rainfall Calculator nor Thetis Tools shows ads.

### Which is updated more often, Rainfall Calculator or Thetis Tools?

Rainfall Calculator ships an update every 29 months, and Thetis Tools every 7 months. Most recently, Rainfall Calculator was updated on September 9, 2026 and Thetis Tools on September 10, 2026.

---

*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*